Correct i saw the series and the biological weapon of choice was Anthrax and Churchill authorized that in the event of an invasion vast quantities of Anthrax would be released along the invasion front. Churchill was fully aware of the civilian casualtie that would eventuate and the political fallout within the populace but was willing to doo all that was available to Britains survival.

And also that the Series did in fact convey that secret British document stated that Britain could not hope to hold off an invasion had the Germans had launched Operation Sealion. Mainly due to the fact that the RAF was running out of trained pilots if the Germans had kept up the pressure on the RAF for two weeks more then the RAF was a spent force, plenty of planes but no one to fly them.

And also i think i have read that the RN heavy units (Battleships, Battlecruisers and Aircraft Carriers) were indeed expressly forbidden to be used in the role of Invasion Fleet interdiction, they were to be expressly used in the transferrence of Royal and Government members and assets to Canada.